The invention relates to an apparatus and a method for processing a surface of a substrate by exposing the surface of the substrate to alternating surface reactions of starting materials. Specifically, the present invention relates to an apparatus for processing a surface of a substrate by exposing the surface of the substrate to alternating surface reactions of at least a first starting material and a second starting material according to the principles of atomic layer deposition method. Particularly, the present invention relates also to a method for processing a surface of a substrate by exposing the surface of the substrate to alternating surface reactions of at least a first starting material and a second starting material according to the principles of atomic layer deposition method.
Atomic Layer Deposition ALD method is based on deposition controlled by a surface, wherein the starting materials are conducted inside an ALD reactor onto the surface of the substrate one by one non-simultaneously and mutually separated. Traditionally starting material is brought onto the surface of the substrate in a sufficient amount so that all available binding sites of the surface will be in use. After each pulse of starting material the substrate will be flushed with inert gas so as to remove the excess of starting material steam in order to avoid the deposition from occurring in the gaseous phase. Then a chemisorbed monolayer of the reaction product of one starting material will remain on the surface. This layer reacts with the next starting material forming a partial monolayer of desired material. The reaction having occurred completely enough an excess amount of this second starting material steam will be flushed with inert gas, so the deposition is based on saturated surface reactions, i.e. the surface controls the deposition. According to a known technique the aforementioned ALD method will be carried in an ALD reactor in which the substrate to be processed is positioned.
One problem in the arrangement according to above described prior art technique is that with ALD reactors it is not possible to process pieces which are so large that they do not fit inside an ALD reactor. This limits considerably the use of the ALD method in many applications. Another problem is that the ALD method is used according to a known technique with vacuum. When depositing for example inner surfaces of containers the container itself may form an ALD reactor in which the vacuum is provided. However, wall thickness of such containers is often not sufficient, and the container may not withstand the necessary vacuum and the container may collapse. Moreover feeding of starting materials successively into large chambers may be difficult and time consuming, since filling and emptying of large chamber is slow. Moreover all the surfaces of the substrate placed in the chamber will be exposed to surface reactions, whereupon it is not possible to expose only part of the surface of the substrate to surface reactions without mounting on the surface of the substrate masks which cover part of the surface of the substrate. However placing of such masks is often slow and complicated.